Such boxes are conventionally provided in aircraft having pressurized cabins in order to provide each passenger with an oxygen mask in the event of an accident leading to a drop in the pressure inside the cabin. Special boxes are thus provided close to the passenger seats, each containing a plurality of masks together with an associated chemical oxygen cartridge or manifold, said cartridge coming into operation when the door of the box is fully opened.
The box may be fully opened automatically or manually by means of a suitable device, and the masks resting on the inside face of the door then fall down and remain suspended at the ends of their supply pipes ready for immediate use by the passengers. Automatic opening by electric or pneumatic means is naturally preferred and may be directly controlled from onboard altimeter equipment. Opening devices are then used of the kind described in published European patent application No. 0 151 063, and such automatic devices must be checked or verified periodically to ensure that they are still operating properly.
Visual inspection may be performed at the same occasion to verify that the oxygen cartridges are operating properly (e.g. by means of an indicator pellet or a circular band).
A distinction is thus commonly drawn between ground inspections of the kind performed every 8000 flying hours, for example, and complete overhauls during which the entire equipment is thoroughly checked, of the kind performed every 12,000 flying hours, as a rule.
It is common practice to provide a device for use during routine maintenance to half open the door and hold it in a position which prevents the masks from falling out, since properly re-packing the masks is a long and tediuos job. The device of half-opening the door must be inconspicuous and relatively difficult to grasp in order to avoid drawing the attention of passengers who might be tempted to operate it.
Presently used devices for half-opening the door (see for example U.S. Pat. No. 4,518,179) are rotatable telescopic systems having a return spring and a bayonet-type latching mechanism. A plate is thus fixed against the far face of the box and carries a slide rod which is terminated by a rectangular block having its outwardly-directed face surrounded by a narrow peripheral rim enabling it to be grasped. An operator must thus use a fingernail or other tool to pull the block against the return force exerted by the spring and then, once the block has been pulled away from the door, the operator must turn it through about 90.degree., thereby enabling it to perform its main function of holding the door half-open.
These devices are robust and very reliable, however they are bulky since the associated plate occupies a certain amount of room inside the box. Bulk is becoming an every-increasing problem particularly when up to eight masks are to be stored in a single box. In addition, operating such devices is not always very easy since the peripheral rim eventually gets worn, making it progressivelly more difficult to graps. Further, the operation is a two-part movement: the block must initially be pulled perpendicularly away from the plane of the door against the return force of the coaxial spring around the rod which holds the block, and then the block must be rotated when fully extended in order to engage the bayonet-type latching mechanism.
Another prior technique consists in providing an independent inspection hatch enabling visual inspection to be performed while leaving the main door in its closed position (see, for example, U.S. Pat. No. 3,503,394). Devices for half-opening doors are frequently preferred to indpendent inspection hatches, either for reasons of expense or else for reasons of convenience.
Preferred implementations of the present invention provide a device for half-opening a door and having a structure which is easy to operate and which occupies relatively little room.
Preferred embodiments of the invention also make it possible to provide access via a larger opening, in particular making it easy to open the box manually in the event that the automatic system does not operate properly.
Preferred embodiments of the invention provide a device for half-opening the door using a minimum of parts, with said parts being simple in structure and capable of being molded.